Conventional incandescent light sources generally convert an electrical current to light by applying a current to a filament, typically made of tungsten, which causes the filament to glow. The filament is generally suspended near the center of a glass bulb, thereby providing light having a radial distribution that can be used to illuminate, e.g., a room. Such conventional incandescent light sources are typically used in chandeliers. Due to the high brightness of the glowing filament (˜1 Mcd/m2), crystals in the chandelier exhibit decorative sparkling light effects. However, the life span of incandescent light sources is typically relatively short, usually limited to the life span of the filament. In addition, the glass bulb generally becomes very hot due to the high temperature of the filament, presenting a potential danger of burning objects that come into contact with the glass bulb.
Replacing incandescent light sources with LED light sources generally alleviates or eliminates the above problems. In addition, such a replacement provides a significant increase in the efficacy, that is the luminous flux produced by the light source as a ratio to the amount of energy (or power) required to produce it. However, most LEDs are only capable of emitting light into a hemisphere (solid angle 2π sr), whereas incandescent light sources employing a glowing filament generally emits light uniformly into a full sphere (solid angle 4π sr).
To overcome this disadvantage, a light source may be provided comprising a cylindrical light guide having a reflector arranged at one end thereof and one or more LEDs arranged at the other end and being situated in a cylindrically shaped cavity having reflecting walls around the LEDs. Such a configuration may allow for achieving a large variety of light intensity distributions of the light source. However, such a configuration in general requires a highly reflective foil or the like to be laminated on the inner walls of the cavity in order to achieve a high optical efficiency for the light source. Another similar approach is to utilize the lower part of the light guide as a reflecting cavity. Thus, according to this approach, the cylindrically shaped cavity housing the LEDs is not required. Such a configuration generally requires that reflective coating is applied to the lower portion of the light guide. Both approaches can be used for achieving a light source having a high optical efficiency.
However, such reflective foils or coatings may increase the cost of the overall device in that additional material as well as additional manufacturing steps may be required. Moreover, the above approaches generally require the dimensions of the light guide to be relatively large, whereas it is generally desirable in lighting design to keep the dimensions as small as possible.